A turbocharged engine applies exhaust gas energy to spin a compressor that pressurizes air supplied to engine cylinders. Compressing air entering the engine elevates intake air temperature. The increased air temperature may decrease engine power by reducing the cylinder charge density. One way to reduce air charge temperature of a turbocharged engine is to install a charge air cooler (CAC) downstream of the turbocharger compressor in the engine's air intake system. Temperature of compressed air entering the CAC is reduced by transferring heat from the compressed air to ambient air or a liquid coolant. Consequently, engine power may be increased by operating engine cylinders with a greater charge density as compared to if the same engine were operated without a CAC. However, air entering the engine may include water vapor that condenses within the CAC when air is cooled within the CAC. If the condensed water is drawn into the engine it may cause combustion instability in the engine. Therefore, it would be desirable to operate an engine in a way that allows the engine to benefit from the CAC with a lower possibility of ingesting condensed water.
The inventors herein have recognized the above-mentioned disadvantages and have developed a method for operating engine compressors, comprising: passing air through a first compressor and a second compressor in an engine air intake; and returning a portion of air passing through the second compressor to the engine air intake downstream of the first compressor and upstream of the second compressor via opening a charge air cooler bypass valve.
By returning a portion of air flowing through a second compressor, it may be possible to increase air flow through the engine air intake system so that condensation may be gradually removed from a charge air cooler without increasing engine torque or significantly increasing fuel consumption. Increased air flow through the charge air cooler allows the air to carry additional water vapor so that water vapor may be gradually inducted into the engine without significantly affecting engine combustion stability.
The present description may provide several advantages. Specifically, the approach may improve engine combustion stability. Further, the approach may reduce accumulation of water within a charge air cooler. Further still, the approach may be selectively applied so that vehicle fuel consumption may not be significantly affected.
The above advantages and other advantages, and features of the present description will be readily apparent from the following Detailed Description when taken alone or in connection with the accompanying drawings.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.